Focus on the Lateral Incisural Space: Where is the Trochlear Nerve?

Area of Science:

• Neurosurgery
• Neuroanatomy

Background:

• The trochlear nerve (cranial nerve IV) is crucial for eye movement.
• Identifying its precise entry point into the tentorium cerebelli is vital for surgical procedures.

Purpose of the Study:

• To define the trochlear nerve's entry point into the tentorium cerebelli.
• To provide topographical descriptions relative to supratentorial and infratentorial landmarks.

Main Methods:

• Analysis of seven formaldehyde-fixed human specimens (14 sides).
• Measurement of distances from established reference points to the trochlear nerve's tentorial entry point.

Main Results:

• The trochlear nerve's cisternal segment and tentorial entry point were consistently identifiable.
• Specific distances were recorded: anterior clinoid process (14-28 mm), posterior clinoid process (9-19 mm), posterior lip of the inner auditory canal (25-29 mm), posterior border of Meckel cave (9-14 mm), and oculomotor triangle (5-16 mm).

Conclusions:

• The trochlear nerve's cisternal length is highly variable, potentially affected by tumors.
• The tentorial entry point serves as a stable landmark for nerve identification during tentorial cutting procedures.